86 PROTOZOA AND DISEASE 



erred in describing as peculiar nucleoli protozoa parasitic in nuclei of 

 other protozoa. The high degree of differentiation in structure and 

 function exhibited by the nucleoli of certain cells, such as ovum- 

 cells, nerve-ganglion-, and epithelial cells, accounts for such errors. 

 In the following studies of sarcoma will be given the writer's 

 ground for thinking that a similar mistake has been made by patho- 

 logists with regard to intranuclear bodies in some sarcomas. The 

 nucleoli in this granulation tissue of the rabbit do not present the 

 distinguishing features of the bodies to be described below as 

 parasites. 



Phagocytosis in Granulation-Tissue Cells. The evidence of phago- 

 cytosis I described as follows : 



' In the neighbourhood of the clot, leucocytes of each variety 

 may be found to have engulfed some of the red 'corpuscles. In 

 the interior of some of the young connective-tissue cells both red 

 and white blood-corpuscles are to be observed. This inception and 

 subsequent digestion of cells and other extraneous particles by living 

 cells is termed phagocytosis.' 1 



Many of the fibroblasts had no nucleolus at all ; in others in 

 Biondi-stained sections there was a condensation of chromatin (net- 

 knots) at one or more points in the nucleus (Fig. 29 ; 7 and 2). In 

 others a central oxyphile body had a marginal part of chromatin 

 which was connected with the general network of the nucleus 

 (Fig. 29 ; 3). In a few the nucleus was poor in chromatin, and 

 several oxyphile bodies were present (Fig. 29 ; 4). All these 

 features point to the nucleolus being a structure from which 

 chromatin is differentiated in the passage of the nucleus from a 

 resting to an active stage ; as such in its simplest forms it would be 

 indistinguishable from the rudimentary forms of certain protozoa. 



1 The significance of the inception of foreign particles by leucocytes was first 

 pointed out by Haeckel ; the bearing of the fact on immunity was indicated by 

 Carl Roser in 1881 ; and the theory of phagocytosis as we know it was fully 

 worked out by Metchnikoff. See G. Sims Woodhead, Transactions of Pathological 

 Society, 1892, p. 20. 



